#include<stdio.h>

int main()
{
	int b, n;
	double s = 0, a = 0.0;
	scanf_s("%d", &n);
	for (b = 1; b <= n; b++)
	{
		a = a + b;
		s = s + 1 / a;
	}
	printf("%lf", s);
	return 0;
}